Personal digital assistant
(PDA) Compact devices used to help organize needed information and services in the hectic lives that most people live in the 21st century. The term Personal Digital Assistant or PDA, can be loosely ascribed to three types of devices: phones, palm-sized devices, and handheld devices. Features between these devices are starting to blend.

Source:
http://www.doncio.navy.mil/iltoolkit/Virtualcomm_PDA.htm